The downside? They’re expensive. Like, really expensive, depending on which one you get. Whether you really need one depends on your budget and how you’re going to be using your ball. For example, I use official match balls for practising freekicks because they fly through the air really nicely. However, I don’t use them for training because if I lose my ball I’ll be set back $100-$300.
Latex bladders are one of the best materials when it comes to ball construction. However, with latex bladders, air won’t last as long as butyl bladders and will need more attention for proper inflation. Butyl-blend bladders hold in the air much better, but they are harder and less receptive in play. Mid-priced balls will usually have a mix of butyl and rubber. https://www.youtube.com/watch?v=c1SVcjYY6TE